Colored television apparatus



93 E. F. w. ALEXANDERSON 1,988,931

COLORED TELEVISION APPARATUS Filed May 2, 1953 Inventor: Ernst F WAIexomdevson,

b 416% His Atto'r'neg.

Patented Jan. 22, 1935 UNITED STATES PATENT OFFICE assignor to General Electric poration of New York Company, a cor- Application May 2, 1933, Serial No. 668,998

Claims. (Cl. 178-6) My invention relates to colored television apparatus and particularly to the receiver of such apparatus. It is the object of my invention to provide an improved receiver for colored tele- 5 vision whose construction is simple and devoid of any moving mechanical parts and which is eflfective to produce a true representation of the view being televised. v

My'invention will be better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

The transmitted signals or impulses which actuate the receiver comprising my invention 15 by which a colored image may be seen may be produced by various well known forms of television transmitting apparatus the only special requirement being that the light received by the photo-electric apparatus in the scanning of the view to be transmitted shall be limited in the scanning of the successive lines respectively to colors which are complementary. For producing the impulses one may employ, for example, the common scanning disk type of transmitter in which alternate disk apertures are covered by filters of one color and the remaining alternate apertures are covered by filters of a color which is complementary thereto. Various other means may be employed if desired for limiting the light received by the light sensitive element of the transmitter to that of one of two complementary colors in the scanning of the successive lines of the view, indeed various other well known forms of transmitting apparatus may be employed but as my present invention relates particularly to the receiving apparatus the description to follow will be confined to that apparatus.

In accordance with my invention I employ a plurality of image producing cathode ray tubes, 40 two in the form of receiver illustrated, one of which responds to the transmitted impulses during the scanning of one set of alternate lines at the transmitter which may be those scanned through a red filter and the other of which responds to the transmitted impulses during the scanning of the other or intervening set of alternate lines which may be those scanned through a green filter. The image produced by one tube then is that due to whatever red may be in the 50 view being transmitted and similarly the image produced by the other tube is that due to whatever green may be in the view. By a suitable optical system the two images are viewed simultaneously the two images being exactly superposed upon each other; also the image by the one tube is viewed through a red filter and the image by the other tube is-viewed through a green filter.

Referring now to the drawing illustrating my invention, Fig. 1 is a perspective view of appara- 5 tus comprising one embodiment of my invention; Fig. 2 represents the ray deflecting wave of the receiver tubes; Fig. 3 shows how the supperposed images on the two tubes would appear, the width of the lines denoting the color, and 10 Fig. 4 is a plan of said apparatus.

In Fig. 1 numbers 1 and 2 represent the enlarged end portions of two image producing cathode ray tubes. These tubes may be of well known construction being provided with end faces 3 and 4 respectively upon which the image is produced, the intensity of the cathode ray of each being varied by the received impulses, and each tube having means such for example as the pairs of plates 3' and 4 shown in Fig. 4 for causing the ray to sweep across the end face of the tube in scanning lines corresponding with those of the transmitter. The scanning lines of the tubes, however, differ from those of the transmitter in that the number of lines of each tube is only one-half the number of lines of the transmitter and the successive scanning lines 01' the transmitter are reproduced alternately by the two tubes. The spacing of the lines of each tube therefore is twice as great as in the transmitter, adjacent lines of a tube corresponding to alternate lines of the transmitter. The above relation of the scanning lines of the transmitter and of the two tubes is effected by employing a single ray defiecting wave for the two tubes which has a frequency per second which is only one-half of the number of lines scanned per second in the transmitter. Such a ray deflecting wave, shown at 5 in Fig. 2, is of the usual saw tooth form but in the present case the amplitude is twice as great as is necessary to cause the ray of either tube to sweep across the end of the tube. The bias of the ray deflecting means of the respective tubes accordingly is adjusted so that the ray of one tube will be swept across its tube end during one-half of each wave and the ray of the other tube will be swept across its tube end during the other half of the wave. The ray of tube 1 for example will be swept completely across the end of that tube during the first half of each wave or from the value a to the mid value b thereof and although further deflection of this my takes place during the second half of the wave, variations in the intensity of the ray during that half of the wave obviously have no effect on the image produced by tube 1. Because of the aforementioned bias adjustment, the ray of tube 2 will not begin to sweep across the end of that tube until the point b is reached in the deflecting wave and a complete traverse will havebeen eifected when the point e is reached, after which the cycle is repeated. Since the frequency of wave 5 is onehalf of that of the number of lines scanned at the transmitter it will be clear that two successive lines are scanned at the transmitter while the deflecting wave 5 rises from a to c and that during the scanning of one line at the transmitter the ray of tube 1 will completely traverse the tube end and during the scanning of the next line at the transmitter the ray of tube 2 will completely traverse that tube end. Thus the image formed by each tube responds only to alternate scanning lines of the transmitter. As it has already been pointed out that adjacent lines at the transmitter are scanned through red and green filters it follows that the image produced by tube 1 is limited to the red portions of the view and the image produced by tube 24s light lines 8, the image made'by tube 2 conesponding to the green part of the view. The, two tube ends may be viewed simultaneously in superposed relation by the use of a partially silvered glass or mirror 9, a.red filter 10 being arranged in front of tube 1 and a green filter 11 in front of tube 2. The two-images then are brought together in proper relation. as shown in Fig. 3, the green square 12 having the red center 13. The light and heavy lines representing the two colors also may be considered as representing the scanning lines of the cathode rays of the two tubes and accordingly are shown alternating with each other, however it should be understood that no attempt has been made to represent the scanning lines in their true spacing.

Instead of employing red and green filters in front of the respective tubes 1 and 2 I may employ cathode ray tubes having diiferent kinds of fluorescent material which will'm'oduce directly the desired colors of red and green. Likewise if the transmitter is of the type which makesuse of cathode ray tubes I may either use colored filters with the tubes or use tubes in which the photo-electric substance is selectively responsive to red and green.

I have chosen the particular embodiment described above as illustrative of my invention and it will be apparent that various other modiflcations may be made without departing from the spirit and scope of my invention which modifications I aim to cover by the appended claims.

What I claim as new and desire to secureby Letters Patent of the United States, is:

1. Receiving apparatus for colored television comprising a plurality of image producing cathode ray tubes, means for producing corresponding deflections of the rays in said tubes alternately to produce alternate lines of the transmitted image with'the intermediate lines blank, the lines produced by one tube alternating with those produced by the other, means, for giving the images produced by the respective tubes complementary colors and means for observing simultaneously the images produced by both tubes.

2. Receiving apparatus for colored television comprising a plurality of image producing cathode ray tubes each including means responsive to the received impulses for producing alternate lines of the image with the intermediate lines blank, the lines produced by one tube alternating with those produced by the other, means for causing the image on one tube to appear red, means for causing the image on the other tube to appear green and means whereby the images on both tubes may be observed simultaneously.

3. In colored television apparatus, a receiver comprising a plurality of cathode ray tubes arranged to be actuated by the same impulses. means for causing the cathode rays alternately to sweep across their respective tubes, means for giving complementary colors to the images produced by the respective tubes and means for simultaneously observing the images produced by the tubes.

' 4. In colored television apparatus, a receiver comprising a plurality of cathode ray tubes arranged to be actuated by the same impulses, each tube having ray deflecting means controlled by a wave having a frequency of onehalf the line frequency of the transmitted impulses, means for giving complementary colors 'tothe images produced by the respective tubes and means for simultaneously observing the images produced by the tubes.

5. In colored television apparatus wherein the transmitted impulses correspond to the light and shade of one color in alternate lines of the view to be transmitted and to the light and shade of another color in the intervening lines of the view, a receiver comprising a plurality of cathode ray tubes arranged to be actuated by the same trans- 

